Chemical Modulation of Orphan Nuclear Receptor Function

孤儿核受体功能的化学调节

• 批准号: 8321788
• 负责人: Sridhar Mani
• 金额: $ 6.93万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-13 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8321788
• 关键词: Adopted; Affinity; Agonist; Antineoplastic Agents; Azoles; Binding; Binding Sites; Biochemical Genetics; Biological Assay; Cell Proliferation; Cells; Chemicals; Clinical; Collaborations; Complement; Complex; Computer Simulation; Coumestrol; Cytochromes; Data; Development; Drug Interactions; Drug resistance; Generations; Genetic Transcription; Goals; Grant; Health; Hepatic; Human; Imidazole; Immune; Ketoconazole; Knowledge; Laboratories; Lead; Libraries; Ligand Binding; Ligands; Mammalian Cell; Mediating; Microsomes; Modeling; Modification; Molecular; Mus; Mutation; Nuclear; Nuclear Orphan Receptor; Nuclear Receptors; Organ; Orphan; Paclitaxel; Pharmaceutical Preparations; Phenotype; Play; Protein Binding; Proteins; Receptor Activation; Receptor Inhibition; Research Personnel; Resistance; Role; Site; Structure; Surface; System; Tamoxifen; Testing; Tissues; Toxic effect; Yeasts; analog; base; cancer cell; cytotoxicity; glycidol; improved; inhibitor/antagonist; monolayer; mutant; novel; pharmacophore; pregnane X receptor; receptor; receptor binding; receptor function; small molecule; tool; yeast two hybrid system

DESCRIPTION (provided by applicant): The central goal of this R01 is to focus on explicitly defining novel antagonist binding pharmacophore on Pregnane X Receptor (PXR). In doing so, additional goals include development of non-toxic azole antagonists that would serve to chemically probe PXR activity and phenotype(s) in different tissues. In silico modeling parameters will continuously be improved as we obtain potent and specific PXR inhibitors. These models could then guide the development of novel small molecule antagonists originating from different chemical entities. The long-term goal is to eventually develop non-toxic antagonists of PXR that can be used as clinical modulators of cancer cell proliferation and drug resistance (e.g., PXR activation induces cancer cell proliferation and drug resistance). It is also hoped that these antagonists will enhance the activity, and minimize the toxicity, of select antineoplastic agents (e.g., tamoxifen, paclitaxel are PXR agonist at concentrations observed at steady-state in humans). Towards this end, we have identified and characterized two novel PXR antagonists, ketoconazole and coumestrol, that specifically disrupt the function of activated (ligand-bound) PXR. In subsequent studies, we have shown that ketoconazole: (i) binds to receptor and disrupts coregulator-receptor interactions in activated PXR; (2) does not displace activating drugs from the ligand-binding pocket of PXR; (iii) retained antagonism of mutant forms of PXR containing ligand-binding pocket filling mutants; and (iv) is unable to antagonize mutant forms of PXR containing alterations in the surface coregulator AF-2 binding site. Thus, we have formulated a model for PXR antagonism in which disruption of function is mediated either by allosteric modification of the receptor or by competition with coregulator binding. We now propose to evaluate this model using structural, molecular, biochemical, and genetic systems to characterize the mechanism by which PXR-directed antagonist ketoconazole and related compounds inhibit receptor activation. PUBLIC HEALTH RELEVANCE: Adopted orphan nuclear receptor, Pregnane X Receptor (PXR), plays a mechanistic role in drug-drug interactions and cancer drug resistance. These functions of the receptor are newly discovered and since this receptor has organ-specific functions, many of its roles in other tissues (e.g., gut) are unknown. PXR is activated by agonists (ligands) and inactivated by antagonists. Our laboratory and co-investigators have taken a lead role in defining novel antagonists of PXR that bind to a region outside the ligand binding pocket. We believe that these antagonists will be necessary to probe PXR function and define all the phenotypes of PXR in mice and humans. In this proposal, we will evaluate our model of antagonism using structural, molecular, biochemical, and genetic systems. These studies will be vital for the generation on non-toxic compounds that antagonize PXR function - a tool necessary to probe PXR function in cells.

描述（由申请人提供）：本R01的中心目标是明确定义孕烷X受体（PXR）上的新型拮抗剂结合药效团。在此过程中，其他目标包括开发无毒的唑拮抗剂，用于化学探测不同组织中的PXR活性和表型。在硅模型参数将不断改进，因为我们获得有效的和特异性的PXR抑制剂。这些模型可以指导来自不同化学实体的新型小分子拮抗剂的开发。长期目标是最终开发出无毒的PXR拮抗剂，可作为癌症细胞增殖和耐药的临床调节剂（例如，PXR激活可诱导癌细胞增殖和耐药）。人们还希望这些拮抗剂能够增强某些抗肿瘤药物的活性，并将毒性降至最低（例如，他莫昔芬、紫杉醇是在人体稳态浓度下观察到的PXR激动剂）。为此，我们鉴定并鉴定了两种新的PXR拮抗剂，酮康唑和库美司醇，它们特异性地破坏了活化（配体结合）PXR的功能。在随后的研究中，我们发现酮康唑：(i)在活化的PXR中与受体结合并破坏协调节因子与受体的相互作用；(2)不会从PXR的配体结合口袋中置换活化药物；（iii）保留了含有配体结合口袋填充突变体的PXR突变体形式的拮抗作用；（iv）不能拮抗含有表面共调节因子AF-2结合位点改变的突变型PXR。因此，我们制定了一个PXR拮抗模型，其中功能破坏是通过受体的变构修饰或与共调节因子结合的竞争介导的。我们现在建议使用结构、分子、生化和遗传系统来评估这一模型，以表征pxr定向拮抗剂酮康唑和相关化合物抑制受体激活的机制。公共卫生相关性：收养的孤儿核受体，孕烷X受体（PXR），在药物-药物相互作用和癌症耐药中起机制作用。受体的这些功能是新发现的，由于这种受体具有器官特异性功能，它在其他组织（如肠道）中的许多作用是未知的。PXR被激动剂（配体）激活，被拮抗剂灭活。我们的实验室和合作研究人员在定义结合到配体结合袋外区域的新型PXR拮抗剂方面发挥了主导作用。我们相信这些拮抗剂将是探索PXR功能和确定小鼠和人类PXR所有表型所必需的。在本提案中，我们将利用结构、分子、生化和遗传系统来评估我们的拮抗模型。这些研究对于产生拮抗PXR功能的无毒化合物至关重要，这是探测PXR在细胞中的功能所必需的工具。